Introduction to Shock and Oxygen Delivery
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Questions and Answers

What occurs when DO2 dips below VO2?

  • Oxygen delivery exceeds oxygen consumption
  • ATP production increases significantly
  • Cellular metabolism shifts to aerobic respiration
  • Some tissues must switch to anaerobic metabolism (correct)
  • What is a consequence of prolonged decreased DO2?

  • Decreased ATP production (correct)
  • Enhanced nervous transmission
  • Increased cellular gradients
  • Decreased intracellular Na+ levels
  • During the compensatory stage of shock, which of the following is usually observed?

  • Grey/purple mucous membranes
  • Bradycardia
  • Hypotension
  • Tachycardia (correct)
  • Which symptom is indicative of decompensatory shock?

    <p>Grey/purple mucous membranes</p> Signup and view all the answers

    What may result from cellular edema in situations of decompensatory shock?

    <p>Cellular necrosis</p> Signup and view all the answers

    What is the primary indicator of shock related to oxygen delivery?

    <p>Increased blood lactate levels</p> Signup and view all the answers

    Which equation represents the oxygen delivery (DO2)?

    <p>DO2 = Cardiac Output x CaO2</p> Signup and view all the answers

    Which component is NOT part of the oxygen content (CaO2) equation?

    <p>Cardiac Output</p> Signup and view all the answers

    What physiological state can occur due to decreased oxygen delivery to tissues?

    <p>Compensatory shock</p> Signup and view all the answers

    What characterizes decompensatory shock?

    <p>Failure of compensatory mechanisms</p> Signup and view all the answers

    How do tissues respond to decreased ability to utilize delivered oxygen?

    <p>Switching to anaerobic metabolism leading to lactate production</p> Signup and view all the answers

    What is the role of hemoglobin in oxygen delivery?

    <p>It carries oxygen from lungs to tissues</p> Signup and view all the answers

    Which factor would most likely lead to decreased oxygen delivery to tissues?

    <p>Low cardiac output</p> Signup and view all the answers

    What is the primary function of capillaries in the oxygen delivery process?

    <p>Facilitate the exchange of gases between blood and tissues</p> Signup and view all the answers

    Which factor is NOT typically associated with increased tissue oxygen demand?

    <p>Cyanide exposure</p> Signup and view all the answers

    What mechanism of cellular respiration does NOT require oxygen?

    <p>Glycolysis</p> Signup and view all the answers

    What is the main consequence of hypovolemia on oxygen delivery?

    <p>Reduced oxygen transport capacity</p> Signup and view all the answers

    Which of the following conditions is considered relatively rare concerning oxygen utilization?

    <p>Cyanide poisoning</p> Signup and view all the answers

    What role does smooth muscle play in the arterioles?

    <p>It acts to regulate blood flow and resistance</p> Signup and view all the answers

    How does an increased surface area in capillaries impact oxygen diffusion?

    <p>Enhances the rate of oxygen diffusion</p> Signup and view all the answers

    What is a key characteristic of aerobic respiration compared to anaerobic respiration?

    <p>It requires oxygen to produce energy</p> Signup and view all the answers

    What is produced from pyruvate during anaerobic metabolism?

    <p>Lactate</p> Signup and view all the answers

    What effect does lactic acidosis have on blood pH?

    <p>Decreases blood pH</p> Signup and view all the answers

    Under normal conditions, what percentage of oxygen is extracted by tissues from blood?

    <p>20-30%</p> Signup and view all the answers

    Which parameter can increase up to 60-70% to meet oxygen demand?

    <p>Oxygen extraction ratio</p> Signup and view all the answers

    What physiological response occurs if delivery of oxygen (DO2) decreases to near or below tissue oxygen demand (VO2)?

    <p>Increased stroke volume</p> Signup and view all the answers

    Which condition is difficult to change quickly without assistance?

    <p>Partial pressure of oxygen (PaO2)</p> Signup and view all the answers

    What measurement can indicate lactic acidosis in the blood?

    <p>Lactate concentrations</p> Signup and view all the answers

    When blood bypasses tissues, what parameter can be falsely increased?

    <p>Oxygen content in the blood</p> Signup and view all the answers

    What is the normal saturation range of hemoglobin (Hb)?

    <p>95 - 100%</p> Signup and view all the answers

    How is oxygen content measured in terms of hemoglobin?

    <p>1.34 [Hb] SaO2</p> Signup and view all the answers

    What does the packed cell volume (PCV) equal in relation to hemoglobin ([Hb])?

    <p>PCV = Hct ⩰ 1/3 [Hb]</p> Signup and view all the answers

    How is cardiac output determined?

    <p>Heart Rate x Stroke volume</p> Signup and view all the answers

    Which factor is NOT mentioned as affecting cardiac output?

    <p>Blood pressure</p> Signup and view all the answers

    What is the effect of decreased oxygen delivery due to lung disease?

    <p>Reduced oxygen availability</p> Signup and view all the answers

    How much oxygen is dissolved in blood per given amount of oxygen partial pressure (PaO2)?

    <p>0.003 PaO2</p> Signup and view all the answers

    Which of the following is a factor that impacts oxygen delivery?

    <p>Both A and B</p> Signup and view all the answers

    Study Notes

    Introduction to Shock

    • Shock is characterized by decreased oxygen delivery to tissues and reduced tissue utilization of delivered oxygen.
    • Objectives for understanding shock include: the oxygen delivery equation, how disruptions in oxygen delivery components lead to shock, physiologic responses to shock, compensatory and decompensatory shock, and blood lactate as an indicator of oxygen delivery.

    Oxygen Delivery (DO2)

    • Oxygen delivery, denoted as DO2, is calculated as Cardiac Output (Q) multiplied by arterial oxygen content (CaO2).
    • Cardiac output is a product of heart rate (HR) and stroke volume (SV).
    • Arterial oxygen content (CaO2) is determined by hemoglobin (Hb), oxygen saturation (SaO2), and dissolved oxygen in the blood (PaO2).

    Oxygen Content (CaO2)

    • CaO2 is a measure of the total oxygen dissolved in the blood and carried by hemoglobin.
    • The formula for CaO2 is 1.34 x [Hb] x SaO2 + 0.003 x PaO2.
    • Factors influencing oxygen content include hemoglobin concentration, oxygen saturation, and partial pressure of oxygen in the blood.
    • Packed cell volume (PCV) is ~1/3 of hemoglobin.

    Oxygen Binding Curve

    • Oxygen saturation (SaO2) and partial pressure of oxygen (PaO2) are related.
    • The relationship is illustrated by the oxygen-hemoglobin dissociation curve, showing the percentage of hemoglobin saturated with oxygen across various oxygen pressures.

    Decreased Oxygen Delivery

    • Factors affecting oxygen delivery include insufficient oxygen in the blood (low oxygen content, lung disease), inadequate tools for oxygen delivery (cardiovascular issues, hypovolemia), and tissue oxygen use.
    • Tissue factors impacting oxygen use include high metabolic rates, increases in body temperature, intense exercise, and cyanide poisoning.

    Oxygen Delivery to Cells

    • Oxygen travels through the circulatory system from the heart to the aorta, then to arterioles, and finally to capillaries (where gas exchange occurs).
    • Capillaries provide a large surface area for efficient oxygen diffusion.

    Cellular Respiration

    • Cellular respiration involves both aerobic and anaerobic processes.
    • Anaerobic respiration, less efficient, occurs when oxygen is limited, producing lactate as a byproduct.
    • Aerobic respiration, more efficient, uses oxygen and occurs in the mitochondria.

    What Happens with Low Tissue Oxygenation?

    • Low tissue oxygenation causes a shift to anaerobic metabolism.
    • Anaerobic metabolism produces lactate and metabolic acidosis.
    • Decreased perfusion and oxygen content lead to reduced oxygen supply.

    Lactate

    • Lactate is produced from anaerobic metabolism.
    • Increased lactate signifies low tissue oxygen levels.
    • Blood lactate measurement can help assess the severity of shock. Values can be measured by using a clinical device or testing the blood.

    How to Estimate Oxygen Demand (VO2)

    • Oxygen extraction ratio (CaO2-CvO2)/CaO2) is a method for approximating tissue oxygen demand.
    • This ratio shows how much oxygen tissues extract from the blood.
    • Normally, this ratio is between 20-30%.
    • Elevated values could indicate an increase in tissue demand for oxygen.

    Aerobic Respiration & Compensation

    • Aerobic respiration (with sufficient oxygen) is important in compensation of lowered oxygen delivery as the body tries to maintain blood oxygen.
    • Compensation includes increased heart rate and output, increased stroke volume and oxygen extraction ratio. Increased heart rate and output.
    • As oxygen delivery declines, compensation eventually fails at which point decreased oxygen delivery transitions into decompensatory shock.

    Decompensatory Shock

    • Decompensatory shock occurs when oxygen delivery (DO2) falls below metabolic oxygen need (VO2).
    • Without sufficient oxygen, tissues switch to anaerobic metabolism leading to lactate build-up, decreased ATP production and cellular gradients.
    • Continued low oxygen delivery can lead to organ dysfunction, necrosis, and other serious outcomes.

    Shock: General Physical Examination

    • Compensatory shock typically presents with tachycardia, tachypnea, and normal or elevated blood pressure.
    • Decompensatory shock often shows bradycardia, tachypnea, grey or purple mucous membranes, and hypotension.

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    Shock - Lecture Notes PDF

    Description

    This quiz explores the critical concepts related to shock, including its physiological responses, the oxygen delivery equation, and how various components impact oxygen supply to tissues. Additionally, it delves into the measures of oxygen content in the blood and their significance in understanding shock.

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